An important factor in the quality control of the building and construction industry is the type of materials that are used. Various methods have been devised and devices produced which are useful in detecting certain types of flaws and defects in conduits and pipe walls. One such method has been the utilization of ultrasound waves to determine the composition of these conduits or pipe walls. Ultrasonic imaging is particularly well suited for this determination since it is quite sensitive to composition, density, elasticity and shape. However, prior known devices can determine these values only if certain variables such as wall thickness are already known. For example, present industrial thickness gauges require prior knowledge of the propagation velocity through the material to be tested.